Planetary gear extruders are used successfully for the compounding and extrusion of thermoplastic plastic materials. One field of application of the planetary gear extruder is in the compounding of polyvinylchloride (PVC) to be fed into a roll nip of a calender for calendering into a film web.
The planetary gear extruder represents a planetary compounding unit in which the main spindle is driven and, as a result, drives the planetary spindles meshing with it and with the internal gearing of the surrounding barrel. At the output end of the planetary gear extruder, a stop ring is arranged coaxially to the main spindle and partially covers the end face of the planetary spindles. The planetary spindles bear against the stop ring, which consequently absorbs the axial forces of these planetary spindles.
The axial forces of the planetary spindles on the stop ring cause, by the dry friction, a great braking effect, which necessitates a high torque for the central spindle, which drives with it the planetary spindles by the common gearing.
Furthermore, due to the braking effect of the planetary spindles against the stop ring, it is necessary to give the central spindle and also the planetary spindles and the stop ring much greater dimensions and to subject them to a special hardening process, because otherwise a disproportionate amount of wear by the gear tooth forces on the two components and on the stop ring cannot be avoided.